linux-kernel - Re: [patch 00/13] Syslets, "Threadlets", generic AIO support, v3

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Date:	Fri, 2 Mar 2007 11:13:23 -0800 (PST)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Evgeniy Polyakov <johnpol@....mipt.ru>
cc:	Ingo Molnar <mingo@...e.hu>, Eric Dumazet <dada1@...mosbay.com>,
	Pavel Machek <pavel@....cz>, Theodore Tso <tytso@....edu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ulrich Drepper <drepper@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@....com.au>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Zach Brown <zach.brown@...cle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Suparna Bhattacharya <suparna@...ibm.com>,
	Jens Axboe <jens.axboe@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch 00/13] Syslets, "Threadlets", generic AIO support, v3

On Fri, 2 Mar 2007, Davide Libenzi wrote:

> And if you really feel raw about the single O(nready) loop that epoll 
> currently does, a new epoll_wait2 (or whatever) API could be used to 
> deliver the event directly into a userspace buffer [1], directly from the 
> poll callback, w/out extra delivery loops (IRQ/event->epoll_callback->event_buffer).

And if you ever wonder from where the "epoll" name came, it came from the 
old /dev/epoll. The epoll predecessor /dev/epoll, was adding plugs 
everywhere events where needed and was delivering those events in O(1) 
*directly* on a user visible (mmap'd) buffer, in a zero-copy fashion.
The old /dev/epoll was faster the the current epoll, but the latter was 
chosen because despite being sloghtly slower, it had support for every 
pollable device, *without* adding more plugs into the existing code.
Performance and code maintainance are not to be taken disjointly whenever 
you evaluate a solution. That's the reason I got excited about this new 
generic AIO slution.

- Davide

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